The
Sparks-Withington Co. was a major player in home radios in the
1920s - the 1950s. The company also manufactured television sets
from the late '30s well into the late 1950s when it sold out to
Magnavox.

Sparton radios were
not you usual run of the mill sets, they were high quality in every
respect. The late 20's models were unique in several ways, not wanting to be a
slave to RCA, they had their own line of vacuum tubes that did not require the
RCA license. Most significant was the unique tuning circuit as used in the above
and other "Equasonne" models. It was well known in the late 1920's that the
superheterodyne circuit was superior in every way than the common TRF circuit.
Sparton Radios incorporated a much improved TRF circuit that was not subject to
RCA patents or license. This circuit (which is basically a tuned filter) was
used in many Sparton models starting in 1928. The unique tuner provided very
precise and selective tuning which consisted of a 4 stages of un-amplified tuned
RF. This was known as the "Technidyne"
circuit, each stage was completely shielded from each other as well
as all external influence. Then
followed a six stage broadband cascade RF amplifier. An improved version of this
tuner was used in a later model 737. The improved circuit was identical in every
respect to the earlier version except an RF amplifier was added in front of the
tuned filter.